Photodynamic therapy (PDT) for skin cancer

• A quick guide to what's on this page
• What PDT is
• When you may have PDT for skin cancer
• How you have PDT

Photodynamic therapy (PDT) is a relatively new type of treatment. It is treatment with a chemical that makes the skin cells sensitive to light. The chemical can be introduced by injecting a drug called a photosensitising agent into the bloodstream. Or it can be applied to the skin in a cream. The drug is absorbed by the body’s cells and makes them sensitive to light. When the area to be treated is exposed to laser light, the cells die off.

In February 2006, the National Institute of Health and Clinical Excellence (NICE) issued guidance on PDT for skin cancers. They say there is good enough evidence to use it for several types of skin cancer. They don't recommend it for squamous cell skin cancers because there is not enough good evidence that it can control the spread of the disease and too high a risk of the cancer coming back. PDT using a cream is now available on the NHS for Bowen's disease, basal cell skin cancers and actinic keratosis (also called solar keratosis).

For skin cancer, PDT is an alternative to surgery. NICE say that PDT is best used in cases where you would need a lot of surgery. So it is best for large skin cancers that are not too deep, or where there are several cancers in an area. PDT is not suitable for deeper skin cancers because the light cannot penetrate far enough into the skin. In the trials NICE looked at, the appearance of the treated area after PDT was better than after surgery. Generally, PDT was as good as surgery at controlling basal cell cancers, actinic keratosis and Bowen's disease in these trials.

To have this treatment, you first have the crust and scale removed from the skin tumour. Then you have a cream that contains the light sensitising chemical applied to the skin cancer and the surrounding area. The cream contains a drug called 5 -aminolaevulinic acid (ALA). Sometimes, you may have the chemical as a tablet or injection. After the doctor or nurse has applied the cream with 5-ALA, that area of your skin will be covered for 3 to 6 hours to allow the drug to get into the skin cancer cells.

The 5-ALA makes the skin very sensitive to light. After it has been absorbed, you will have a strong light shone on to the treated area for up to 45 minutes. The light will kill any cell that has absorbed the 5-ALA. You can have more than one skin tumour treated at a time and can have the treatment more than once.

All the treatment can be done in out patients. You must keep the treated area covered and dry for 36 hours, but after that it is fine to bathe or shower if you treat the area gently. It will scab over and the scab falls off on its own about 3 weeks later. If you have a thick skin lesion, you may need another treatment about 4 weeks later.